The prevalence of adaptive travel adaptors (TA) and fast chargers is increasing due to the popularity of mobile electronic systems. In an adaptive TA system, a traditional flyback power converter operates as a power stage with a protocol Integrated Circuit (IC) providing an interface between the TA and a sink device (e.g., a mobile phone, or device that “sinks” current supplied by the power converter). Typically, the protocol IC receives and decodes a command sent from the sink device, and in response, the adaptive TA system changes an operating characteristic of the power converter.
The changes to the operating characteristic can be implemented at the secondary side of the adaptive TA system, however from a power stage optimization perspective it is preferred to be implemented at a primary side, to realize a truly adaptive power delivery based on a power request from the sink device.
Conventional adaptive TA systems use an optical isolator (e.g. optocoupler) for transferring a protocol message from the secondary side to the primary side, thus increasing cost and reducing system reliability. The secondary side protocol IC receives the protocol message from the sink device, encodes and sends the protocol message to the primary side through the optical isolator. The primary side control IC receives the encoded protocol message from the optical isolator, further decodes the message and responds by changing an operating characteristic of the TA system from the primary side. Because the protocol IC is located at the secondary side, a reliable and cost effective circuit and method are needed to realize effective communication between the secondary side and primary side in the adaptive power system.